The present disclosure relates to processes for producing toners suitable for electrophotographic apparatuses.
Numerous processes are within the purview of those skilled in the art for the preparation of toners. Emulsion aggregation (EA) is one such method. These toners may be formed by aggregating a colorant with a latex polymer formed by emulsion polymerization. For example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in its entirety, is directed to a semi-continuous emulsion polymerization process for preparing a latex by first forming a seed polymer. Other examples of emulsion/aggregation/coalescing processes for the preparation of toners are illustrated in U.S. Pat. Nos. 5,403,693, 5,418,108, 5,364,729, and 5,346,797, the disclosures of each of which are hereby incorporated by reference in their entirety. Other processes are disclosed in U.S. Pat. Nos. 5,527,658, 5,585,215, 5,650,255, 5,650,256 and 5,501,935, the disclosures of each of which are hereby incorporated by reference in their entirety.
EA toner processes include coagulating a combination of emulsions, i.e., emulsions including a latex, wax, pigment, and the like, with a flocculent such as polyaluminum chloride and/or aluminum sulfate, to generate a slurry of primary aggregates which then undergoes a controlled aggregation process. The solid content of this primary slurry dictates the overall throughput of the EA toner process. The solids content of the primary slurry is conventionally between about 11% and about 14%. While an even higher solids content may be desirable, it may be difficult to achieve due to high viscosity of the emulsions and poor mixing, which may lead to the formation of unacceptable primary aggregates (high coarse particle content).
Experimental data has shown that the aggregation step generally includes two stages. In the first stage, the primaries come together to form small clusters about 1-3 microns in size (i.e., aggregates). This stage is relatively fast (i.e., the process typically completes in about 5 minutes). For the second stage of aggregation, the so-formed 1-3 micron sized clusters further aggregate into 5-8 micron toner sized particles. The process speed of this second stage is relatively slow. In the past, there have been various theories/hypotheses for the explanation of this process. Whatever the reason, the long process time increases the cost of manufacturing and limits the rate of throughput of a toner plant.
Consequently, improved methods for producing toners, which reduce the number of stages and materials, remain desirable. Such processes may reduce production costs for such toners and may be environmentally friendly.